Name: gas pressure patterns in kinetic molecular theory
Uploaded: 2020-09-03T13:38:27.000Z
Duration: 2 min 34 s
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Kinetic Molecular Theory and Gas Laws Explain Properties of Gas Molecules

Obserwacje różnych właściwości gazów, wyrażone przez różne prawa gazu wyprowadzone przez Boyle'a, Charlesa, Gay-Lussaca i Avogadro, wynikają koncepcyjnie z kinetycznej teorii molekularnej.

Ciśnienie wywierane przez gaz wynika z oddziaływania stale poruszających się cząstek na ścianki jego pojemnika.

Zmniejszenie objętości pojemnika, przy jednoczesnym utrzymaniu stałej liczby moli i temperatury, zbliża cząsteczki gazu do siebie, zmniejszając ich odstępy między cząstkami.

W tej mniejszej objętości zwiększa się gęstość gazu i częstotliwość zderzeń – częstotliwość zderzeń molekuła ze ścianą. W związku z tym wzrasta ciśnienie wywierane przez gaz. Odwrotna zależność między ciśnieniem a objętością jest określona przez prawo Boyle'a.  

Dodanie większej ilości moli gazu do pojemnika w stałej temperaturze zwiększa gęstość gazu, a co za tym idzie, częstotliwość zderzeń. 

Aby utrzymać ciśnienie początkowe, objętość musi się rozszerzyć. Ten bezpośredni związek między objętością a pieprzykami wynika z prawa Avogadro. 

Teraz weź pod uwagę, że liczba pieprzyków jest utrzymywana na stałym poziomie , a temperatura wzrasta. Ponieważ średnia energia kinetyczna cząstek gazu wzrasta proporcjonalnie do temperatury, cząstki zderzają się ze sobą częściej i z większą siłą.

Jeśli objętość jest utrzymywana na stałym poziomie, podczas gdy temperatura wzrasta, gęstość gazu i częstotliwość zderzeń wzrastają, a co za tym idzie, ciśnienie również wzrośnie. Bezpośredni związek między ciśnieniem a temperaturą jest określony przez prawo Gay-Lussaca. 

Z drugiej strony, jeśli ciśnienie musi pozostać stałe wraz ze stałą liczbą moli, to wzrostowi temperatury musi towarzyszyć wzrost objętości, aby rozciągnąć zderzenia na większą powierzchnię. Ten bezpośredni związek między objętością a temperaturą jest określony przez prawo Charlesa. 

Wreszcie, zgodnie z kinetyczną teorią molekularną, cząsteczki gazu nie przyciągają się ani nie odpychają od siebie. W mieszaninie różnych gazów składniki działają niezależnie , a obecność innego gazu nie ma wpływu na ich indywidualne ciśnienia. 

Całkowite ciśnienie mieszaniny jest zatem sumą poszczególnych ciśnień cząstkowych. To jest prawo Daltona.

kinetyczna teoria molekularna i prawa gazowe opisujące właściwości cząsteczek gazu

Testem teorii kinetyczno-molekularnej (KMT) i jej postulatów jest jej zdolność do wyjaśniania i opisu zachowania gazu. Różne prawa gazowe (prawa Boyle’a, Charlesa, Gay-Lussaca, Avogadra i Daltona) można wyprowadzić z założeń KTM, które przekonały chemików, że jej założenia dokładnie odzwierciedlają właściwości cząsteczek gazu.

<h4>Kinetyczna teoria molekularna wyjaśnia zachowanie gazów</h4>

Przypominając, że ciśnienie gazu wywierane jest przez szybko poruszające się cząsteczki gazu i zależy bezpośrednio od liczby cząsteczek uderzających w jednostkową powierzchnię ściany w jednostce czasu, KMT koncepcyjnie wyjaśnia zachowanie gazu w następujący sposób:

Prawo Gay-Lussaca: Jeśli temperatura wzrasta, wzrasta średnia prędkość i energia kinetyczna cząsteczek gazu. Jeżeli objętość utrzymuje się na stałym poziomie, zwiększona prędkość cząsteczek gazu powoduje częstsze i silniejsze zderzenia ze ściankami pojemnika, zwiększając w ten sposób ciśnienie. Nazywa się to również prawem Amontona.

Prawo Charlesa: Jeśli temperatura gazu wzrośnie, stałe ciśnienie można utrzymać tylko wtedy, gdy zwiększy się objętość zajmowana przez gaz. Spowoduje to większe średnie odległości pokonywane przez cząsteczki, aby dotrzeć do ścianek pojemnika, jak również zwiększoną powierzchnię ścianek. Warunki te zmniejszą zarówno częstotliwość zderzeń cząsteczek ze ścianami, jak i liczbę zderzeń na jednostkę powierzchni, czego połączone efekty równoważą efekt zwiększonych sił zderzenia ze względu na większą energię kinetyczną w wyższej temperaturze.

Prawo Boyle’a: Jeśli objętość gazu się zmniejsza, powierzchnia ścian pojemnika maleje, a częstotliwość zderzeń cząsteczek ze ścianami wzrasta, co powoduje wzrost ciśnienia wywieranego przez gaz.

Prawo Avogadra: Przy stałym ciśnieniu i temperaturze częstotliwość i siła zderzeń cząsteczek ze ścianami są stałe. W takich warunkach zwiększenie liczby cząsteczek gazowych będzie wymagało proporcjonalnego zwiększenia objętości pojemnika, aby uzyskać zmniejszenie liczby zderzeń na jednostkę powierzchni, kompensując zwiększoną częstotliwość zderzeń.

Prawo Daltona: Ze względu na duże odległości między sobą cząsteczki jednego gazu w mieszaninie bombardują ścianki pojemnika z tą samą częstotliwością, niezależnie od obecności innych gazów, a całkowite ciśnienie mieszaniny gazów jest równe sumie ( cząstkowe) ciśnienia poszczególnych gazów.

Kinetyczna teoria molekularna i prawa gazowe opisujące właściwości cząsteczek gazu

Sprawdzianem kinetycznej teorii molekularnej (KMT) i jej postulatów jest jej zdolność do wyjaśnienia i opisania zachowania gazu. Różne przepisy dotyczące gazu ...

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gas pressure patterns in kinetic molecular theory

Kinetic molecular theory explains gas pressure by linking it to the motion of gas molecules. Gas pressure comes from rapidly moving molecules hitting the walls of a container. It depends on how many molecules strike a unit area in a given time.

The theory also helps explain the main gas laws. In Gay-Lussac’s law, also called Amontons’s law, raising temperature increases the average speed and kinetic energy of gas molecules. If volume stays constant, the molecules collide with the walls more often and more forcefully, so pressure increases.

Charles’s law shows what happens when temperature rises at constant pressure. The gas must expand to keep pressure steady. That larger volume means molecules travel farther before reaching the walls, and the wall area increases too. These changes lower collision frequency and the number of collisions per unit area, which balances the stronger collisions caused by the higher kinetic energy.

Boyle’s law describes the effect of smaller volume. When gas volume decreases, the container wall area also decreases. Molecule-wall collisions become more frequent, and the pressure rises. Avogadro’s law says that at constant pressure and temperature, the collision rate and collision force stay constant. If the number of gas molecules increases, the volume must increase in proportion so the collisions per unit area can drop enough to offset the added molecules.

Dalton’s law applies to gas mixtures. Because gas molecules are far apart, one gas in a mixture strikes the container walls with the same frequency whether other gases are present or not. The total pressure of the mixture equals the sum of the partial pressures of the individual gases. These gas laws show how the assumptions of kinetic molecular theory fit the behavior of gases.

Gas Pressure Patterns in Kinetic Molecular Theory

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kinetic molecular theory and gas laws explain properties of gas molecules

Kinetic molecular theory explains gas pressure by linking it to the motion of gas molecules. Gas pressure comes from rapidly moving molecules hitting the walls of a container. It depends on how many molecules strike a unit area in a given time. The theory also helps explain the main gas laws. In Gay-Lussac’s law, also called Amontons’s law, raising temperature increases the average speed and kinetic energy of gas molecules. If volume stays constant, the molecules collide with the walls more...

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key terms and concepts

Explore how kinetic molecular theory explains gas pressure, temperature, volume changes, and the gas laws of Boyle, Charles, Gay-Lussac, Avogadro, and Dalton.

Gas Pressure Patterns in Kinetic Molecular Theory | JoVE K12

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Gas Pressure Patterns in Kinetic Molecular Theory

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